Automatic riveter



June 33, 11950 J. 0 HRUBY, JR

AUTOMATIC RIVETER Filed March 7, 1944 2 Sheets-Sheet l INVENTOR.

AGENT June 13, 11950 J. o. HRUBY, JR

AUTOMATIC RIVETER 2 Sheets-Sheet 2 Filed March 7, 1944 INVENTOR. JUHN ZZHEU Yh/k.

AGENT Patented June 13, 1950 UNITED STATES TENT OFFICE AUTOMATIC RIVETERJohn 0. Hruby, In, Glendale, Calif., assignor to Lockheed AircraftCorporation, Burbank, Calif.

12 Claims.

This invention relates to automatic riveting machines in general, andmore particularly to the automatic control of machines for upsettingrivets in pre-punched or pre-drilled sheet metal parts in the mannercommonly employed for riveting airplane skin panels, and the like.

lhis invention may be adapted to numerous uses, but finds its principalapplication in automatic riveting tools wherein an electrical contactmade with an unset rivet located in place in the part to be rivetedinitiates and controls the riveting action. The present invention isprimarily directed to the form of riveting tool involving rapidautomatic actuation and control, together with suitably safety mechanismwhich allows actuation of the machine only when the pre-punched ordrilled sheets containing the unset rivets in place in the rivet holehave been located precisely in the correct position in the machine,between the riveting punch and anvil, and the prevention of inadvertentoperation of the dimpler prior to such proper location of the work, andalso to prevent inadvertent repetition of the riveting operation at asingle riveting location.

This invention thus finds one of its most important applications in thefabrication of sheet metal airplane parts which require the rivetingtogether of one or more super-imposed parts or sheets usually ofextensive size and area such .as a wing or fuselage panel requiring alarge number of rivets, often placed in long rows, in which the rivetholes have been previously punched or drilled, and in which the rivetsare previously inserted in place in such holes preparatory to theirrapid successive upsetting.

Various forms of riveting tools have been heretofore employed for usewith either one shot or diaphragm types of rivet squeezers. Ascustomarily operated, these rivet machines have a foot switch or airvalve to be manually actuated by the operator after he has located thrivet within the center of the riveting punch and anvil.

With such manual operation of the squeezer mechanism it is possible forthe machine to be actuated prior to proper location of the work sheetcarrying the rivet in the machine, or during the step of shifting thework sheet to adjust the rivet to the proper position from one workposition to another, and thus inadvertent operation of the machine oftenoccurs accidentally, apparently due to momentary lapses of propercoordination of the operator, probably brought about by the fatigueassociated with rapid operation. Such inadvertent operation of themachine usually results in serious damage to the work piece, and attimes, injury to the operator.

t is accordingly an object of this invention to eliminate the usualmanual controls employed for Operation of the rivet squeezer, and toreduce the time consuming and tedious manipulation required to properlylocate the rivet within the squeezer, thereby reducing fatigue andgiving the operator greater freedom of movement and facility of handlingthe work sheet applied to the riveting machine.

It is another object of this invention to pro-v vide an automaticriveting machine, through which the pre-punched or pre-drilled partscontaining inset rivets may be rapidly fed, and by which setting of eachrivet will be automatically and rapidly effected when each rivet in thework sheet reaches the proper-location in the machine.

It is a further object of this invention to provide means forfacilitating the guidance of the rivets in the parts to be riveted tothe proper location within the riveting machine. It is a still furtherobject to furnish a practical safety means to prevent inadvertentactuation of the machine while the work sheet containing the rivets isimproperly located. It is a still further object of the presentinvention to provide automatic actuation of the machine of suchcharacter as will produce uniform setting of rivets independent of theskill of the operator.

The objects are attained in general by an embodiment of the inventionwhich includes an automatic mechanism associated with the die whichrenders the squeezer machine inoperative unless the rivet carried in thework sheet is in its precisely correct position between the die and. thepunch, and which will then substantially automatically initiate theaction of the punch when the work sheet carrying the rivet is solocated.

The objects of this invention are also attained by novel electricaltiming and control means associated with the before mentioned automaticdie mechanism.

These and other objects and features of novelty will become evidenthereinafter in the description, which together with the followingdrawings, illustrate preferred embodiments of the invention.

Figure 1 is an elevation of a typica1 squeeze riveting machine showingthe general arrangement of the apparatus of this invention therein.

Figure 2 is an enlarged front elevation of they automatic riveting headassembly as viewed on line 2-2 of Figure 1.

Figure 3 is a plan view of the automatic riveting head assembly as takenon line of Figures 1 and 2.

Figure is a side elevation of the automatic riveting head of Figure 2and including a schematic representation of an ass ciated electriccontrol circuit.

Figure 5 is a fragmentary side elevation view of the automatic rivetinghead of Figure 4 at one of the stages of its operation.

Figure 6 is a schematic wiring diagram of an alternative control andtiming circuit.

Referring now to the drawings in which like reference numerals refer tocorresponding parts throughout the several figures, the apparatus of theinvention is as follows:

The apparatus of this invention as employed in connection with aconventional pneumatic squeeze! machine is shown in Figure 1, saidmachine comprising a yoke it having upper and lower jaws I! and 52supported on a pedestal 13. On the upper jaw ii is a diaphragm cylinderI' l, the diaphragm piston of which operatively connected throughsuitable linkages to the 'reciprocable punch holder it. The automaticriveting head including the riveting anvil which comprises a principalpart of the invention, may be mounted in either jaw of the pneumaticsqueezer, but has been shown for convenience as supported in the lowerjaw of the squeezer yoke in operative position as shown at it aligneddirectly beneath the said punch it. In operation the pro-punched ordrilled sheet carrying the unset rivets inserted in place in the holes,is introduced into the machine between the punch and anvil set as shownat H in Figure 1. If the rivet-- ing head is placed in the upper jaw itis necessary to invert the work sheet, and under such condition therivets previously inserted in the hole may be retained in place by meansof ad hesive paper tape. Air under pressure from a suitable source issupplied to the diaphragm cylinder is by pipes it and is, through apilot operated control valve 2; The pilot valve 29 is adapted to becontrolled by the variation of low pressure air in pipe 22 by a-solenoidoperated air valve V as hereinafter more fully described.

The electric timing and control circuit is contained within a box 25mounted on the squeezer pedestal l3, and the before mentioned solenoidcontrol valve is housed in a box 26 which may be placed in anyconvenient location. Low pressure air is applied to the solenoid valve Vin box 25 from a suitable source through pipe 2?. The electric wiresinterconnecting the electric control circuit and the solenoid operatedvalve pass through a suitable shielded conduit as shown at 28. Theelectrical conductor from the electric control circuit in box 25 passesthrough a suitable shielded conduit 23 to a terminal box 38 into whichthe lead conductor ill extending from the automatic riveting head itmakes a plug connection as shown at 32.

7 Referring nowprimarily to Figures 2 to 5, the body of the automaticriveting head comprises a cylindrical shank 40 carrying an integrallyformed, upwardly extending threaded spindle 4| terminating at the topend in an anvil surface 42. The shank ill is adapted to fit into thecylindrical holding recess in the lower jaw l2 and to retain theautomatic riveting head in an upright position in alignment with theriveting punch holder l5 asbest shown in the assembly of Figure the in land in cross-sectional detail in Figures 2 and 4.

A yoke carrying an integrally formed cylindrical guide shoe member to isreciprocably supported on the upper portion of the stem i! The guideshoe has a bore adapted to make a slidable. fit over the unthreadedupper end of the stem t! adjacent the anvil surface 52, and two oppositecylindrical segrnental top portions normally extend a suitable distancethereabove as best shown at in Fi ures 2 and l. A pin l! fixedtransversely through the stem extends laterally through oppositelongitudinal slots formed in the sides of the guide shoe body, whichserve as stops to limit the axial movement of the said yoke and guideshoe on the stem. A. coil spring 49 surrounding the stem ll and actingunder compression against an adjusting nut 55) threaded on the lowerportion of the stem ll and against upper surface of the yoke d5, servesto urge the yoke and guide shoe to the fully extended position aslimited by the before men- "ioned pins a: slots as best shown at Theupper portion of the cylindrical guide shoe it has a forwardly directedV-shapecl guide opening extending down from the top end thereof to apoint 3-3 a substantial distance below the top surface of the anvil asnormally positioned, the opening being formed in effect by removal of acylindrical segm nt as best shown at all in Figures 2 and 3.

A slot is formed in the rearward top portion of the guide shoe shown at5'8 opposite to the said forwardly directed V-shaped guide opening 55,of a suitable size to receive the tapered end portion of the movablecontactor arm 55 which is described hereinafe A Ushapcd hinge instraddles the lower portion of the is pivotally conns of oppositelypositioned Attached to the 1 "e member 5-2, and

pivotally supported tactor arm The laterally extending portion 56 of thearm 55 is formed with a diagonal cam surface tapered inner end of whichnormally extends over the upper end of the anvil 42 through the beforementioned rearward slot- 58 formed in the guide shoe. he said camsurface is constantly urged inward into contact with the curved outer ofthe anvil as shown at point iii in Figure by of the leaf spring which isattached to the yoke at 62, and inwardly against the arm at 63. Theforward end the which normally extends c or the upper surface of theanvil =32 is formed l a J depression or guide as show; at The iii-53 ispreferably oi nbre or pie ier suitable insulatin material and ca beddedtherein, as shown at an e"ectrical conductor. The said electricalconductor is positioned to extend or project from the end of the contactarm 55 centrally within the guide depression of the contact guide asshown. at 653, to form a small contact electrode. The conductor carriedwithin the contactor arm is connected by an insulated conductor throughplug-32 and connector box to the e ectronic control equipment ashereinafter more y describe Referring now nar l to Figure i in whichhereof are as follows: T1 and T2 are vacuum tubes which maybe ofsubstantially anyo'f the Well known suitable types. For example, a type6N7 tube which is a twin triode containin the elements of the two tubesin one envelope, may be advantageously employed, although forconvenience, two separate tubes are herein illustrated. S1 and S2 aresingle pole double throw and double pole single throw magnetic relaysrespectively. C1 and C2 are condensers, and R1, R2, R3 and R4 areresistors of suitable values. The high voltage supply for the plates ofthe vacuum tubes is supplied from a suitable source, such as, forexample, a battery B which may be of approximatel 150 volts D. C., and anegative grid bias is obtained from a suitable battery C which may beapproximately 5 volts. Suitable variation in these voltages may be madeas is well known in the art.

The operation of the automatic riveter in combination with theelectronic control circuit of Figure 4 is as follows: When the rivetermechanism is not in operation and the electronic circuit is quiescent,the vacuum tubes T1 and T2 are maintained non-conductive, or at a lowconductivity, by reason of their grids G1 and G2 being biased to cut-on,or close to cut-oiif, potential by the battery C. Under this initialcondition, the condenser C1 is charged to a voltage at or approximatelythe grid cut-ofi potential of tube T1 as just stated. Upon inserting thework sheets I! containing rivets between the punch and anvil of theautomatic riveter and bringing a rivet as shown at 15 through the guideV 5! and into contact with the electrode 65 in the end of the contactorarm as best shown in Figure 4, the charge on condenser C1 is dischargedthrough the limiting resistance B2, conductors 14 and 61, contact 85,and thence through the rivet shank and through the automatic rivetinghead mechanism to ground 16. Resistance R1 being relatively high, thebattery C cannot immediately restore the charge in condenser C1. Thegrid G1 or the tube T1 is thus lowered to substantially cathodepotential which immediately renders the tube T1 sufficiently conductiveto operate the relay S1. The resultant current flow from battery Bthrough the tube T1 from cathode to anode and through the electro-magnetof the relay S1 and return through conductor H, moves the relay armature18 into contact with point 19. The grid G2 of vacuum tube T2 is thusnext connected to ground through conductor 80, relay armature 18,conductor 8!, condenser C2 and connection 82. The condenser C2 havingbeen previously bridged by resistance R3, which is connected to ground84-82, the grid G2 is thus also next reduced to substantially cathodepotential which immediately renders the tube T2 sufiiciently conductiveto operate the relay S2. The timing constant of the circuit comprisingC2 and resistance R4 is such that the grid G2 will not immediatelyreturn to cut-off potential. This time delay period may be adjustedbetween suitable limits by means of the variable resistance R4. Upongrounding the grid G2 through the condenser C2 as before mentioned, theresultant flow from cathode to anode through the vacuum tube T2 andthrough the electro-magnet of the relay S2 causes the interlinkedarmatures 85 and 86 to be moved into contact with the points 81 and 88respectively. Upon thus closing the contact between armature 86 andcontact point 88, an electric circuit is completed through the solenoidS by way of conductors 99, 9| and 92, whereby the current flows throughand actuates the solenoid from a suitable source which may be connectedto the circuit at 9.3 and 94.

6 1. The resultant actuation of the valve V through linkage 95 by meansof the solenoid S, causes air pressure to be applied to cylinder Hi, andthe rivet punch Hi, to be lowered forcefully into contact with the headof a rivet and to upset the shank thereof against the anvil 42 in themanner hereinbefore described in connection with Figure 1 and as bestshown at 95 in Figure 5. Simultaneously, upon completing the circuitupon energizing relay S2, the relay armature is moved into contact withpoint 81. As the riveting punch 55 is lowered into contact with the headof the rivet, force is applied through the rivet and through the sheetI! to the top member 44 of the guide shoe t6, and the continued downwardmotion of the punch 15 in upsetting the rivet against the upper end ofthe anvil 42 as shown in Figure 5, results in corresponding downwardmovement of the yoke 45 against the force of the spring as, carryingwith it the arm 55. The resultant downward motion of the arm 55 with theyoke 45 causes relative motion between the cam surface 51 and the edgeof the anvil 6 3, such as to rotate the arm contactor 55 clockwise aboutthe hinge centers 53 a sufficient distance to remove the cammed endportion out of its initial position in slot 58 between the punch l5 andanvil 2 to the new position shown in Figure 5. The contactor arm may bewithdrawn by suitable electric, hydraulic, pneumatic or mechanicalmeans, an example of the latter means comprising the cam Bil beingherein shown as a preferred construction. The contact between electrodetie and the shank of the rivet is thus broken immediately after theinitial completion of the circuit therethrough and the guide 54 carryingthe electrode 65 is removed from a position adjacent the rivet duringthe upsetting of the rivet. Meanwhile, however, the connection thusbroken at 53 has been shunted by the relay S2 as hereinbefore described.This latter step in the operation of the circuit insures completion ofthe riveting cycle regardless of how brief the contact of electrodes @6with the rivet may have been. In other words, the relay S2 actingthrough armature 85 temporarily locks the vacuum tube T1 in a conductivecondition for a predetermined adjustable period of time by maintainingits grid G1 at ground potential through the circuit comprising conductorM, contact 3?, armature 85 and ground connection 95.

After a period of time, the length of which is dependent upon theconstant of the timing circuit comprising the resistance R4 and thecondenser C2, as hereinbefore mentioned, the potential of the grid G2 intube T2 will return to its cut-off value by flow of current from batteryC through R4, whereupon this tube will be rendered non-conductive. Theresultant cessation of flow of current through the relay S2 will then inturn allow the armatures 85 and 8t 01" relay S2 to return to the initialposition shown opening the circuits at contacts i3? and $3. Thefollowing resulting de-energization of the solenoid S will allow valve Vto return to its normal position and the punch IE to rise to its openposition after having completed the upsetting of the rivet. After thebreaking of the locking-in circuit at contact 81, and after apredetermined adjustable period of time determined by the constants ofthe timing circuit for the tube T1 comprising the condenser C1 and thevariable resistance R1, the grid G1 of tube T1 will return to itscut-cit potential by flow of current from battery C through R1. Thefollowing resultant cessation of. current through the relay S1 will thenallow the 7. armature 1'3. to return to the position shown,reestablishing contact with point 53v and thereby discharging condenserC2 to ground potential in readiness for the next operating cycle.

The time constant of the timing circuits R1Cl. and R4C2 may be adjustedto suit theparticular operating condition obtaining by variation ofeither the resistances or the capacities in-the manner well known bythose skilled in the art. However, adjustment of the constant of these;timing c cults may be most conveniently made by employin suitable vaiable resistances in R1 and R4.

The values of R1 and Cr may be approximately 500,000 to 1,060,000 ohmsand 6.5 microfarad respectively for a of approximately 0.3 to 0.6; secorThe values of R4 and C2 may be approximately 759,050 ohms and 0.5microiarad respectively for a period of approximately 0.1 to 0.5 second.

Referring now to 8, an alternative electronic control circuit isdiagrammatically illustrated, the principal components of which are asfollows: T3 is a suitable vacuum tube which may be, for example, a type865 triode, S3 is a double relay, C3 is a concle r, R5 and Re areresistors of suitable values. The high voltage supply for the plate ofthe vacuum tube is supplied from a suitable source such as battery B, asdescribed hereinbefore in connection with Figure l. Various commonground connections are shown throughout the circuit. The operation ofthe apparatus of this invention in conjunction with the electroniccontrol circuit of Figure 6 is as follows: Prior to grounding theelectrode 5% through an introduced rivet mile the squeezer mechanism isnot in operation, the electronic circuit is quiescent and the vacuumtube T3 is in a nonconductive or low conductivity condition by reathe gd Gs biase son to. the this co to cut-oil" or close 6], c l armatureI21, and current limiting. resistance R2, t; charge on condenser 03 isimm iately 1o" "ed to ground and cathode poneighborl cod 0 rec te ohmsand the con .enser C1 of tely 0.5 microiarad, the butt '3; C cannotimmediately restore the charge in condenser 03, the grid G of the tubeT1 is thus lor-Jered to substantially cathode potential whichimmediately renders it sufficiently conductive to actuate the relay S3.

The resultant current flow from battery B through the tube Ts fromcathode to anode and through the electro-magnet of the relay S3 andreturn through conduct r ieL-l, moves the relay armature iiil away fromcontact with point [Eli and simultaneously moves the armature Hi lintocontact with point Upon thus closing the contact between armature i3 3and contact point it ctric circuit is completed through the solcnconductors 1&6, Hill and [38 whereby a c. t may flow therethrough from asuita which may be connected at I59 resultant operation of valve Vcauses the rivet-er punch E to 0 contact with the rivet head as beiowere hereinbeiore described.

After a predeta 8 thelength of which is dependent upon the constantof.the timing circuit comprising the before mentionecl'variable resistanceR5, and the condenser C2, the grid G connected thereto returns tocut-offpotential, or to a potential which will result in sufficientreduction of the plate current to release the relay S3. The resultantcessation or reduction or" current flow through the relay S3 allows'thearmatures lili and his to return to I the positions shown, breaking thecircuit through the solenoid S re-establishing contact of the armatureldl with contact point not, thereby again connecting the control circuitto the contact in readiness for the next riveting cycle. Simultane usly,upon thus opening the circuit through the solenoid S the valve V returnsto its off position, thereby actuating the pilot valve 21! to exhaustthe air from the diaphragm cylinder i i and to allow the punch to rise,completing the operating cycle of the machine.

As the force of the riveting punch 15 is removed from the top of thehead of the rivet, the guide shoe it also rises upward on the spindle llunder the force of spring is, carrying with it the U- shaped hingemember 52 and the arm 5556. The arm i i-5% under the force of the leafspring or moves inward from the position shown in Figure 5 to that shownin Figure 4 maintaining contact between the cam surface 5? and the edgethe anvil at point 66. lChe electrode 85 in the guide depression Ed isthus reset in its initial position adjacent the center of the anvil inreadiness for contact with the next rivet shank to be led into positionfor riveting.

As before stated, the present invention has for one or." its advantagesthe elimination of the foot- "l etofore employed for either the initia-The n of the manual control of the riveter ted in the removal of aprincipal source ie for the operator. Heretofore the uniio-rr v thequality of riveted connections produceo by the machine when manuallycontrolled, were dependent largely upon the manner of mating thecontrol; thus slow, light pressure on th foot pedal or other manualcontrol produced insuiiiciently upset rivets, while fast, su den, orheavy pressure produced too great an upset on the rivets. The productionof perfectly set rivets heretofore required intense concentraticn, andsuch coordination of eyes and feet as obviously resulted in sufficientnerve strain and fatigue to result in a substantially reduced ratenotion, with frequent poorly set rivets, tin es, damage to the sheetmetal parts the operations were being performed. mage also often beendone to the parts riveted, and also to the machine by which st was beingperformed by rough operor the actuation of the riveting tool. elimi ahas r o. of unskilled workmen.

ther particularly important feature of this ith electronic control meansactuated by cont at with the cart upon which the work is to be periorrer... s sakes the device practical connection with the use of aluminum,particularly an vd aluminum rivets, which ordinarily an coating.sufiiciently resistant to other electric contact and actuation sinoperative.

re apparatus of the present invention, due ct that no manualcoordination or operation ot. er t ..an feeding the work materialcontaining the rivets into the machine is required,

and by reason of the fact that it is impossible to actuate the riveteruntil the rivet in the work sheet is precisely positioned on the rivetanvil in alignment with the rivet punch, anyone without previousexperience can produce perfectly riveted joints at a high productionrate. Also, positively and uniformly set rivets will always be produceddue to the uniform pressure obtained. While the present automaticriveting control is illustrated for use with a riveting tool, it isobvious that it may be employed in connection with any similar tool.

The electronic circuit of Figure 4 may be advantageously employed forcontrol of other similar machines, one such machine lor which it isparticularly well suited, being shown and described in the ChristensenPatent No. 2,438,842, which issued March 30, 1948, from an applicatic-nfiled of even date herewith.

It is to be understood therefore that the foregoing is not to belimiting, but may include any and all -forms of method and apparatuswhich are included within the scope of the claims.

I claim:

1. In an automatic riveting tool, apparatus comprising a riveting punch,a riveting anvil in alignment therewith, a movable guide sleeve adjacentsaid anvil, and normally extending above the surface of said anvil andadapted to support a work piece containing a rivet to be set, a movableelectrode associated with said sleeve and normally located intermediatesaid punch and anvil surfaces, and adapted to contact a rivet placed insetting position therebetween, means actuated by relative movementbetween said anvil and said sleeve to move said electrode from itsposition between said punch and anvil, and electrical control means incircuit with said electrode and adapted to be energized by the contactof said electrode with said rivet to actuate said punch.

2. In an automatic riveting tool, apparatus comprising a riveting punch,a riveting anvil in alignment therewith, a movable guide sleeve carriedon said anvil and normally extending above the surface of said anvil andadapted to support a work piece containing a rivet to be set, a movableelectrode hinged to said sleeve and normally located intermediate saidpunch and anvil surfaces and adapted to contact a rivet place in settingposition therebetween, means actuated by relative movement between saidanvil and said sleeve imparted by said punch to move said electrode awayfrom its position intermediate said punch and anvil surfaces, andelectrical control means in circuit with said electrode to actuate saidpunch.

3. Apparatus according to claim 2 in which the means actuated byrelative movement between said anvil. and said sleeve comprises a camsurface associated with said electrode and adapted to move in contactwith the anvil.

4. In an automatic riveting tool, apparatus comprising a riveting anvilbody, a retractable guide sleeve reciprocably supported on said anvilbody and normally extending above the working surface thereof, a springurging said guide sleeve in said extended position, an arm hinged tosaid guide sleeve and supporting an electrode adjacent the workingsurface of said anvil, said electrode being adapted to make electricalcontact with a rivet to be set when said rivet is properly positioned onsaid anvil bcdy, a cam surface associated with said arm and actuated bysaid anvil to move said arm relative to the said anvil working surfaceupon retraction of said sleeve on said anvil body, and means to retractsaid guide sleeve upon said anvil body against the force of said springduring the setting of a rivet.

5. In an automatic riveting tool, apparatus comprising a riveting anvilbody, a retractable guide sleeve reciprocably supported on said anvilbody and having a portion normally extending above the working surfacethereof adapted to support a work piece containing a rivet to be set, aspring urging said guide sleeve in said extended position, an arm hingedto said guide sleeve and supporting an electrode adjacent the workingsurface of said anvil in a position adapted to make electrical contactwith a rivet placed in setting position thereon, a cam surfaceassociated with said arm and actuated by said anvil to move said armaway from the said anvil working surface and to break said electricalcontact upon retraction of said sleeve upon said anvil body, a n d punchoperated means to impart movement from a work piece placed upon saidportion of said guide sleeve to retract said guide sleeve upon saidanvil body against the force of said spring during the setting of arivet.

6. Apparatus according to claim 1 and a slot in the upper end of theguide sleeve adapted to receive and guide a rivet to a setting positionover the anvil surface.

7. Apparatus according to claim 4 and a slot in the upper end of theguide sleeve adapted to receive and guide a rivet to a setting positionover the anvil surface.

8. Apparatus according to claim 1 and a guide associated with said armand said electrode adapted to position a rivet over the working surfaceof said anvil.

9. Apparatus according to claim 4 and a guide associated with said armand said electrode adapted to position a rivet over the working surfaceof said anvil.

10. An electronic timing control apparatus comprising a first vacuumtube having a grid, means to charge said grid to bias it to anonconducting state, a timing circuit electrically connected with thegrid of said first vacuum tube and arranged to render said first vacuumtube conductive for a predetermined time when said timing circuit isenergized, a second vacuum tube having a grid, means to charge said gridto bias it to a non-conducting state, a timing circuit electricallyconnected with the grid of said second vacuum tube and arranged torender said second vacuum tube conductive for a predetermined period oftime, a first relay electrically connected to said first vacuum tube andsaid second timing circuit and so arranged that when said first vacuumtube is rendered conductive by its timing circuit said first relaycloses the second timing circuit to said second vacuum tube whereby torender the latter conductive for a predetermined period of time, asecond relay electrically connected to said second vacuum tube and soarranged as to be closed by the second vacuum tube when the latter isconductive, said second relay being electrically connected in the firsttiming circuit in such a way as to lock said first timing circuit out ina condition to render said first vacuum tube conductive so long as saidsecond vacuum tube is conductive, a switch closed by said second relaywhereby to actuate the apparatus to be controlled, and switch meanscarried by said controlled apparatus arranged to initially close saidfirst timing circuit to render said first vacuum tube conductive.

ii 11. An electronic timing control apparatus comprising a first vacuumtube having a grid, means to charge said grid to bias it to anunconducting state, a circu nected with the grid of said fir andarranged to render said conductive for a predeter timing circuit isenergized, a second vacuum tube having a grid, means to charge said gridto bias it to a non-conducting state, a timing circuit electricallyconnected With the grid of said second vacuum tube and arranged torender said second vacuum tube conductive for a predetermined period oftime, a first relay electrically ccnnec c. to said first vacuum tube andsaid second timin circuit and so arranged that when s id first vacuumtube is rendered conductive by timin circuit said first relay closes thesecond timin circuit to said second vacuum tube whereby t render thelatter conductive for a predetermined period of time, a second relayelectrically connected to said second vacuum tube and so arranged as tobe closed by the second vacuvn tube When the latter is conductive, saidrelay being electrically connected in t n ing circuit in such a as tolock s ing circuit out in a condition to reuse vacuum tube conductive solong as ea vacuum tube is conductive, a switch said second relay wherebyto actuate to (no-1 nrst closed .paratus to be controlled, switch meansarranged to momentarily close said first circuit to render said firstvacuum tube conductive.

12. An electronic timing control apparatus comprising a vacuum tubehaving a grid, an electric circuit for chargin said grid W1 ereby tonormally maintain said vacuum tube non-conductive, a timing circuitincluding the grid of s lid vacuum tube and so arranged when closed asto render said vacuum tube conductive for a predetermined period oftime, a relay electrically in circuit with said vacuum tube when thelatter is i2 rendered conductive, an electric circuit arranged to beclosed by said relay when the Vacuum tube is conductive, said lastmentioned circuit being anged to ctuate apparatus to be controlled, aswitch also arranged to be actuated by said relay luain said timingcircuit in an activated n to render said vacuum tube conductive for apredetermined period of time, and means associated with said apparatusto be controlled and with said switch including an electric circuit fromsaid apparatus to said timing circuit arbe opened to "isconnect s idtiming circuit from said apparatus during the period of time when saidvacuum tube is conductive.

JOHN O. HRUBY, JR.

JI'QDZES are of record in the N Mergcnthaler Jan. 17, 1833 Thomson Feb.25, 1896 Pratt Jan. 11, 1910 Robert Apr. 18, 1916 Henry Apr. 27, 1925Rippl Sen 29, 1936 Adair Aug. 10, 1937 Goodl'ing et al July 9, 1940Butter Sept. 17, 1940 Rockwoocl, Jr Jan. 13, 1942 Mort] Feb. 1, 1944Fischer et a1 Aug. 8, 1944 Sekella liar. 13, 1945 Rechtcn et ai. Mar.2'7, 1945 Gsborne 1 May 29, 1945 Tiffany Oct. 23, 1945 Christensen 1948Country D 7,379 Great Britain Apr. 3, 1930

